diff --git a/aarch64/Dockerfile b/aarch64/Dockerfile
index 800cdc4..7db6b85 100644
--- a/aarch64/Dockerfile
+++ b/aarch64/Dockerfile
@@ -1,4 +1,4 @@
-FROM arm64v8/ubuntu
+FROM arm64v8/ubuntu:20.04
 
 RUN set -eux; \
     apt-get update; \
diff --git a/templates/aarch64.Dockerfile b/templates/aarch64.Dockerfile
index 296c606..5d47949 100644
--- a/templates/aarch64.Dockerfile
+++ b/templates/aarch64.Dockerfile
@@ -1,4 +1,4 @@
-FROM arm64v8/ubuntu
+FROM arm64v8/ubuntu:20.04
 
 RUN set -eux; \
     apt-get update; \